Sized Points on a Map
This example visualizes global cities with populations over 50,000 using sized points on a natural Earth projection. City locations and population data come from a Simplemaps world cities CSV, while country boundaries are rendered from World Atlas TopoJSON. The React app uses `d3.geoNaturalEarth1` and `d3.geoPath` to draw graticules, landmasses, and interiors as SVG paths, then scales circle radii with `d3.scaleSqrt` based on population. Semi-transparent circles encode population density, creating a clear global distribution pattern.